The present invention relates to a cassette and a handling system having the same.
Recently, liquid crystal displays (LCDs), especially thin film transistor liquid crystal displays (TFT-LCDs), as a kind of flat panel displays, are increasingly becoming popular. In a LCD, a color filter substrate and an array substrate which are assembled together are essential parts for manufacturing a LCD. Both of the substrates are made by using a thin glass plate as a base. During manufacturing a LCD, unprocessed glass plates, processed glass plates, or assembled panels are always needed to be carried to somewhere. Especially, during manufacturing an array substrate (thin film transistor substrate), there are a number of processes, which each involve some apparatuses of different functions, for example, a processing apparatus for processing the plates and carrying apparatus for loading and/or unloading the plates, and so on.
In a conventional method, a cassette is often used as an apparatus for storing and carrying glass plates. Such a cassette 100 is shown in FIG. 1, which comprises a top plate 101 and a base plate 102 with posts 103 arranged between the top plate 101 and the base plate 102. The posts 103 are arranged on three sides of the plates 101 and 102 so as to define a space for operation, leaving one side open for handling glass plates 200. Support beams 104 are arranged on the inner side of the posts 103 facing the inside of the cassette 100 and supporting the glass plate 200 thereon, and the support beams 104 may be a single beam connected between two opposite posts 103 or a short bar projected from the side of each post 103, respectively, as long as they can support the glass plate 200 thereon. In operation, the cassette 100 usually cooperates with a handling desk 300. The handling desk 300 comprises a base platform 301 for placing the cassette 100 and a recess for picking up and/or placing of the cassette 100 with an apparatus such as a forklift. The handling desk 300 is usually fixed to the ground beside the processing apparatus. After the cassette 100 is carried and placed on the handling desk 300, the glass plates 200 housed in the cassette 100 can be picked up and placed on the processing apparatus for further processing.
The cassette may be typically provided with a plurality of support beams at different levels, so that glass plates can be placed on the support beams at different levels and carried between various processing apparatuses simultaneously. That is, the glass plates housed in a same cassette can be carried and processed together until they become finished products after various steps, thus improving productivity. Therefore, during processing, storing and carrying, the several glass plates in the same cassette can be regarded as a whole.
However, during transporting or carrying, vibrations and unexpected shakes give rise to a degree of position offset for the glass plates. The position offset may accumulate among the processions so that the glass plates may go beyond the bounds of processing, bringing about mismachining tolerance. The cassette of the above design is designed only for the purpose of loading and unloading glass plates and can not adjust the position of the glass plates even if there is position offsets of the glass plates. In order to cope with the problem, a position adjustment device is provided for the glass plates in the processing apparatus and brings a limited position adjustment for the glass plates before processing. Generally, such position adjustment device is incorporated into a carrying robot, a carrying apparatus, or the processing apparatus as an additional apparatus such as a pusher or a clamper, intending to keep the position offsets of the glass plates within the bounds of processing.
In order to clearly show the position offsets of the glass plates during transporting, experiments have bee made. Table 1 shows a set of experiment data, which denotes the measured values of the position offset of the glass plates during three long distance transportations of the cassette.
TABLE 1SlotIDA1A2A3B1B2B3C1C2C3D1D2D3113.51414.51010.511.599.510.511.510.51021010.511.56.56.5129.51010.51514.5931111.5126.57129.591014.513.58.54131313.577.512.5899.512.511.511512.51111.588.59.51010.59.514.513.514611.511.51188.59.511.51213.514.51414.571212.512.587.5910.51111.513.5131381312.51388.5910.51111.512.512.51291313138.599.51011111212121014141488.59.59.59.510.511.51111111414148.58.591010.51111.511.511121414148.58.59111111.511.511.511.513131313.5991011.511.5121211.5121413.51313888.51010.51111.51212151413.5148.598.510.510.51111111116131312.57.57.57.510.5111111.51212171413.513.588.58.59.5101111.51110.51814141488.58.5111012.511.510.51019141413.578.588.59.510.51110.510.52014.51414.5788.59.59.59.510.510.59.5
In Table 1, entries A, B, C and D represent the measured values of the distance between the edge of the glass plates 200 and the edge of the cassette 100 at LA, LB, LC, and LD, respectively, as shown in FIG. 2, and the numbers following A, B, C and D represent the times of transportation, respectively; the sequence numbers in the column correspond to the glass plates in the cassette, and the less the number, the lower the corresponding glass plate is positioned in the cassette.
The above table records the accumulated position offsets at the four measuring sites for each of the twenty glass plates carried in the cassette. The unit of the position offset in the table is millimeter (mm). The table shows that the glass plates tend to shift to the outside of the cassette, and the glass plates at different levels have different position offsets. Furthermore, the table shows a phenomenon that some glass plate may experience a relative bigger “jump” after a certain transportation, which makes the glass plate shift outside of the position adjustment capability of the processing apparatus and accordingly may result in an industrial accident.
Thus, it needed to reduce the position offsets during the transportation of the glass plates, especially, in manufacturing a LCD.